After Minnesotans overwhelmingly went for Obama in the DFL caucuses on Feb. 5, she still didn't endorse anyone, but she hinted that Obama's win would factor into her decision.

Klobuchar's support is key this year because, as a senator, she's also a superdelegate. That means she'll get a vote at the party's convention this summer, where it seems ever-more likely that the votes of superdelegates will be needed to seal a nomination for either Obama or Clinton.

Klobuchar, who is a year older than Obama, compared the Illinois Senator to the late Hubert Humphrey, a former Minnesota senator and vice president. She saids Obama speaks "with a different voice, bringing a new perspective and inspiring a real excitement from the American people."

Her endorsement comes just days after Obama picked up the support of another Senate Democrat, Bob Casey of Pennsylvania.

"Barack has been a proven agent for change and advocate for middle-class Americans," Klobuchar added. According to the Obama campaign, Klobuchar is the 64th superdelegate to endorse him since the Feb. 5th Super Tuesday contests.